GS450 2 into 1 Exhaust Lengths?

[lake_harley]

A few years ago I fabricated a pretty neat (I thought anyway) 2 into 1 exhaust system for a CB175 Honda. I want to fabricate one now for a GS450 I have. Like the Honda system, the one for the Suzuki will be built using mandrel bends and straight tube, all butt-fitted and TIG welded together.

When I built the first exhaust I got some input from someone who had some racing experience to get an idea of what primary lengths and tube diameters would work well on the street. I'm not out to gain every last HP available, but would like a system that is sized (length and tube diameter) for good performance at "highway" RPM (probably more low to mid range power), rather than a race intended system for maximum power at high RPM.

Anyone have experience they'd be willing to share?

Thanks, in advance.

Lynn

 

[jfman]

Well Pete's exhaust is pretty sweet and readily available.

 

[lake_harley]

Can't say I'm familiar with the exhaust you mentioned, "Pete's exhaust". I did a google search and didn't really find a website. Probably I'm not looking correctly.

In reality though, I'd like to build my own system for three reasons; 1) I'm a fabricator, 2) I enjoy it, 3) I can do it for less $$ than buying a exhaust system. The last 2 into 1 I did only cost about $50-60 in materials.

Lynn

 

[SVSooke]

http://www.thegsresources.com/_forum/search.php?do=finduser&u=446&starteronly=1 This is pete's started threads,his pipes should be in there.

 

[koolaid_kid]

There is a member on here who's handle is Pete. He is an Aussie. He has a 450 with a custom exhaust. It reminds me of the Street Scrambler exhausts of old. Go to the twin section and find his posts and take a look at his exhaust. However, I understand your question and I am not sure his was built with your questions in mind; diameter, length, etc. to maximize efficiency and tune to a particular bandwidth.

 

[tom203]

Maybe this link will work- scroll down a bit

http://www.thegsresources.com/_forum/showthread.php?t=158670

 

[lake_harley]

Thanks for the last three posts. I found the exhaust system on Pete's build thread....looks like great work. I'll read a little deeper into his build to see if there's any mention of tube length or diameter.

If I have this picture posting thing figured out, hopefully there will be a picture of my 175 and the exhaust I built. I'd like to build something similar for my 450. Just looking for the length and diameter input for tubing selection.

 

[koolaid_kid]

You can always PM him. He is a very active and helpful member of this forum.
Nicely done 175. I always liked the style of that bike, although at the time I was a very dedicated 2 stroke rider.

 

[barnbiketom]

Nicely done 175. I always liked the style of that bike, although at the time I was a very dedicated 2 stroke rider.

funny you say that 'kid..

you took the words right oughta my mouth hahahah.. dam RDs

 

[koolaid_kid]

funny you say that 'kid..

you took the words right oughta my mouth hahahah.. dam RDs

Hehe. I had two of them. Nothing like blowing away a single cam Honda 750 to bring a smile to your face.

 

[Guest]

Hey mate, I'm Pete with the exhaust haha

I did actually take some measurements for someone a little while back but I can't recall the thread where I posted them now so I would have to go and take them again.

However, my exhaust was done purely for aesthetic reasons (I love scrambler style pipes) and was not tuned performance wise or anything like that, although it seems to perform just nicely for what I need! I had a local exhaust shop here make it for me (Tranzac).

There is another member on here that gave me some measurements for a tuned 450 2 into 1 system that would probably suit what you're looking for, and I'm pretty sure that was GregT. Shoot him a PM. Unfortunately I deleted the PM after I had mine made...

 

[lake_harley]

Thanks for stepping up Pete! I'll try to do some searching for the info about the "tuned" system you mentioned. As I said early on, I'm not out for every last HP the bike has potential of making, but I'd like to build a system that has some "design" to it so at least I don't kill any power. My goal is similar to your's, mostly appearance, with probably a side benefit of significant weight savings over the stock system.

I appreciate your reply.

Lynn

 

[Guest]

No problems at all Lynn, happy to help if I can.

Found the thread with my measurements in it too:

http://www.thegsresources.com/_forum/showthread.php?t=199065&highlight=exhaust+diameter

Post #9, and don't forget they're very approximate and apologies for the filthy bike

 

[lake_harley]

Wow! Thanks Pete. That will be a great help. That's a nice looking exhaust system!. I have to admit cheating and looking at the "Inches" side of your caliper to see ~1 1/2" diameter. That's just about what the stock pipes on my 450's measured and I just happen to have a couple 1 1/2" mandrel "J" bends on my shelf and some 1 1/2" X .062" tubing. How convenient! I'll convert the lengths from metric to inches and compare to the stock pipes just before they go into the muffler. I'll have to look back to see if the picture shows if you started your measurement at the flange.

I'm probably making it sound like I'm making a big deal about the measurements. I'm not, really. Just hoping to not "kill" any power. When I did the 2 into 1 for my 175 Honda I was cautioned to not use too large a diameter pipe, or, if I recall correctly, it would take power away from the low RPM range and move it higher...just to opposite of what I'd want for street riding I'd think. Did you notice any change in your bike by the "seat of the pants" or otherwise?

Thanks again!

Lynn

 

[koolaid_kid]

Just an old hot rodder interjecting, you are correct. Do not go too large of diameter or you will lose low end power, not a good thing on a 450. Now that you know the diameter, to tune the length, you want to do 2 things: try to make the total length of each pipe as close to equal as possible, and position one pipe such that it draws the exhaust out of the other. This is called equal length tuning. Works for street cars, anyway.
You'll see what I mean when you get there.
I'm done interrupting. Thanks.

 

[lake_harley]

koolaid kid....you're not interrupting. Old hot rodder here too. If my fuzzy memory serves correctly a longer primary will retain low/mid RPM power, and for top end power the primaries get shorter....or is it the other way around. Oh well I have a 50/50 shot at making power somewhere along the RPM range:lol:.

Somewhere, I have a book that had a formula to use as a starting point for tube diameter and length based on engine displacement and the desired RPM range the exhaust was to be most effective. Where that book is is anybody's guess. I've searched some on the internet for similar info but didn't locate anything I found helpful. Maybe my searching skills are weak.

Working out pipe routing can get interesting to achieve equal length. On the Honda system I got the lengths within about 1/2" of being equal and called it good at that. Also, here's a picture of the merge collector I built. The primaries could be fitted to the angled outlets on the head individually and then the collector slipped into place.

I just saw the barely visible 23 1/2" notation in sharpie on the lower pipe in the picture. I'm guessing that was my primary length, at least on that tube.

Lynn

 

[koolaid_kid]

You are correct on the primary length, but you won't have to worry about that since you have to wrap around the engine and under/past the rider. Have you decided whether you are going low or high? I really like Pete's scrambler-style pipe, but most go for the low style. Most go down and to the right, Pete went high and to the left. Just thinking out loud.
If you look at examples of 4 cylinder headers, they do fancy stuff with the routing of each pipe to make them as equal of length as possible and meet in the collector at relatively the same place.
Took me a minute to see that you joined between the peg and the frame. Does the peg get a bit toasty?

 

[SVSooke]

I'm going to throw another consideration into the mix.Engine configuration and exhaust timing because of it.I'm not sure how the 175 you worked on is set up put the later 400 Honda's was a 360 degree design with the pistons going up at the same time.Meant that the exhaust pulses are (IRRC)360 degrees apart.The GS450 is a 180 degree engine with the pistons "rocking".The exhaust pulses in this configuration are 180 and 540(?) degrees apart.The 360 engine will lends it's self to a 2>1 much better than the 180 does.Might just want to look at doing a 2>2 instead.Not saying a 2>1 will not work OK but a 2>2 might be better for power.
Edit:I might have the math wrong,early here and my math is not good at best.Hope you get what I mean inspite of that.

 

[Guest]

I'm not going to even pretend to know what I'm talking about with exhaust tuning

My headers aren't even as the measurements show, but that was never going to happen with the scrambler style...

Because it's a high pipe going under my ankle/shin, I had it ceramic coated rather than chromed and that definitely makes a huge difference to the outside temperature it runs at.

If you are going to go high, you're definitely going to have to go left instead of right if you still want to be able to check your oil level. Going high also means no issue with side stand or centre stand clearance.

My initial cardboard mock up was on the right and it was all good until I saw the dipstick... no way was it coming out with the exhaust on that side.

The only potential issue with it on the left was getting to the choke lever on the carb's, but I already had made an adaptor and used a later GSXR left control to get a 'bar mounted choke lever so that was no issue. In the end I think it would've been fine anyway, but I hate the lever on the carbs.

Interestingly enough, with the new pipes and K&N's, the seat of my pants says definitely more get up and go, and it gets going probably 500RPM's lower than with the stock setup. Used to have to be 5 - 5.5K RPM for her to really get going, now more like 4.5 - 5K.

 

[lake_harley]

Thanks again for the replies and thoughts. My plan would be a low exhaust system, only since that's my preference.

I was aware of the 180* firing rather than 360*, but I'm not sure how that might affect exhaust design. Thinking maybe one cylinder might get scavenged more than the other by the un-even firing I guess? Good question. More research might be in order.

2 into 2 would be a piece of cake....hardly worth doing anything other than stock. We can't have that....can we?

On the 175 there was barely enough room to thread the two primaries through the gap between the peg/frame/engine. I hoped, if anything, it wasn't too close to the engine from a heat standpoint, but I never noticed any heat issue on the peg, even on a 560+ mile weekend ride.

Thanks, as always.

Lynn